<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">

    <!-- 引入react核心库 -->
    <script src="https://unpkg.com/react@17/umd/react.development.js"></script>
    <!-- 引入react-dom，用于支持react操作DOM -->
    <script src="https://unpkg.com/react-dom@17/umd/react-dom.development.js"></script>
    <!-- 引入babel，用于将jsx转为js -->
    <script src="https://unpkg.com/@babel/standalone/babel.min.js"></script>
    <!-- 引入prop-types -->
    <script src="https://cdnjs.cloudflare.com/ajax/libs/prop-types/15.8.1/prop-types.min.js"></script>
    <title>01-渐变动画案例</title>
</head>

<body>
    <!-- 准备好一个"容器" -->
    <div id="root"></div>
    <script type="text/babel">
        //创建组件
        //生命周期回调函数 <=> 生命周期钩子函数 <=> 生命周期函数 <=> 生命周期钩子
        class Life extends React.Component {

            state = { opacity: 1 }

            death = () => {
                //卸载组件
                ReactDOM.unmountComponentAtNode(document.getElementById('root'))
            }

            //组件挂完毕
            componentDidMount() {
                console.log('componentDidMount');
                this.timer = setInterval(() => {
                    //获取原状态
                    let { opacity } = this.state
                    //减小0.1
                    opacity -= 0.1
                    if (opacity <= 0) opacity = 1
                    //设置新的透明度
                    this.setState({ opacity })
                }, 200);
            }

            //组件将要卸载
            componentWillUnmount() {
                //清除定时器
                clearInterval(this.timer)
            }

            //初始化渲染、状态更新之后
            render() {
                console.log('render');
                return (
                    <div>
                        <h2 style={{ opacity: this.state.opacity }}>React学不会怎么办？</h2>
                        <button onClick={this.death}>不活了</button>
                    </div>
                )
            }
        }
        //渲染组件
        ReactDOM.render(<Life />, document.getElementById('root'))
    </script>
</body>

</html>